Baal worship entered Israel through Jezebel, a Phoenician princess from Sidon who married King Ahab of Israel (1 Kings 16:31). She brought her native religion with her and actively promoted the worship of Baal and Asherah in the northern kingdom, even maintaining 450 prophets of Baal and 400 prophets of Asherah at her own table (1 Kings 18:19).
Jehu was actually the king who destroyed Baal worship in Israel by killing the prophets and priests of Baal and demolishing the temple of Baal (2 Kings 10:18-28). Omri was Ahab's father and, while he did evil in God's sight, the introduction of Baal worship is specifically attributed to the influence Jezebel brought through her marriage to his son. Obadiah was a devout servant of God who hid and protected 100 prophets of the Lord from Jezebel's persecution (1 Kings 18:3-4).